A space sensor layer represents a central component of both reinvigorated attention in space operations and the reality of renewed great power competition. Unfortunately, the current pace for acquiring it is something less than the speed of relevance. Despite frequent statements of support from the Pentagon, its realization faces architectural, budgetary and institutional impediments.

The emergence of hypersonic missiles is an important feature of renewed strategic competition. Over the past 15 years, Russia and China invested in these new kinds of strike systems, which pose a different kind of threat to U.S forward forces, bases and power projection. Hypersonic glide vehicles and scramjet cruise missiles are designed to circumvent both intercept by missile defenses and detection by satellites that support strategic warning.

The indispensable requirement for contending with hypersonic threats is the ability to see them. Whereas the highly predictable arc of a ballistic missile requires a shorter period to determine its trajectory and impact point, the flight path of a maneuvering hypersonic missile is decidedly unpredictable. Continuous, birth-to-death tracking is therefore necessary to maintain custody of the threat, whether to determine its target, hand off information to interceptors to try to engage it or simply to provide strategic warning so U.S. forces can attempt evasion. Doing so over the horizon demands sensors in space.

The Hypersonic and Ballistic Tracking Space Sensor, or HBTSS, program will fill this gap. Its purpose is to track both emerging hypersonic missiles and today’s ballistic missile threats, such as intercontinental ballistic missiles fielded by North Korea. Speaking at the Center for Strategic and International Studies in January, Vice Chairman of the Joint Chiefs of Staff Gen. John Hyten expressed concern about HBTSS’ relatively slow pace of development, urging that we need to stop “studying the heck out of it” and move more aggressively on testing.

Three obstacles impede faster progress on this program: a plan for the overall architecture, adequate funding and the institution building the sensor payload.

The Pentagon’s preferred approach, pioneered by Dr. Michael Griffin, under secretary of defense for research and engineering, is a proliferated constellation in low-Earth orbit, with more sensors than an adversary would be able to attack or suppress. Resilience is a critical attribute in the face of high-end threats. But LEO alone may not be enough. Hyten suggested that different orbits might be desirable, too, including medium-Earth orbit.

In December 2018, Griffin also acknowledged the desirability of being “as widely distributed over as many choices of orbital regimes as we can effectively use.” But thus far, plans remain exclusive to LEO. This is the right near-term focus, but multiple orbits will be crucial for longer-term success.

The second concern is budgetary. Despite stated enthusiasm for the capability, the Trump administration’s funding requests in both 2019 and 2020 were negligible — just $15 million in 2020 — and it fell to Congress to raise funding to $73 million and $108 million, respectively. The president’s budget request for 2021 dipped again by about 10 percent, to $99.5 million. Future years remain unclear, given the lack of transparency in open budget documents.

A third issue is which institution is best suited to develop the sensor payload. Oddly, the 2020 budget request moved HBTSS from the Missile Defense Agency and gave it to the Space Development Agency, an entity that was still being created at the time of the request. On a bipartisan basis, Congress responded by insisting it remain with MDA.

The National Defense Authorization Act that assigned HBTSS to MDA was signed by President Donald Trump in December 2019. But when the president’s 20201 budget request was submitted just two months later, it contained another effort to transfer it out. At a March 12 hearing of the House Armed Services Committee, congressional leaders of both political parties grilled Pentagon witnesses about the administration’s attempted move.

The Pentagon would be wise to heed Congress’ bipartisan resolve here. SDA has a great deal to do, including develop the broad architectural plan; figure out how best to transport massive amounts of data across and within the several layers; determine how to effectively configure the design satellite bus for size, weight, power and bandwidth; and then cost-effectively orbit large numbers of satellites.

That is a big enough checklist for a new organization, especially one whose future seems uncertain.

The concern in Congress and elsewhere is that critical mission-specific characteristics might get lost in the shuffle. Public reports and budget documents hint that the mission may be down-scoped, weakening its focus to chiefly hypersonic gliders at the expense of ballistic missile threats already here today — effectively taking the “B” out of HBTSS.

Whatever savings might be had from such a move would likely be eclipsed by expensive investments in other ground-based sensors for ballistic missile defense. Let MDA develop the sensor payload, and let SDA figure out everything else.

Melanie Marlowe is a nonresident senior associate at the Center for Strategic and International Studies.

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